The present invention relates to an air cleaner provided with a fuel adsorption member for adsorbing a fuel vapor leaking from an intake system of an engine.
This kind of air cleaner is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2001-263177, Japanese Laid-Open Patent Publication No. 2001-336454 and Japanese Laid-Open Patent Publication No. 2003-42017.
The air cleaner described in Japanese Laid-Open Patent Publication No. 2001-263177 is provided with sheet-like fuel adsorption members 101 including an active carbon having a fuel adsorbing function, as shown in FIGS. 13 and 14. The fuel adsorption members 101 are arranged downstream of a filter element 102, and is attached within a housing 104 in a hanged state. In this structure, at an engine stop time when an intake air E does not exist, the fuel adsorption members 101 are in a hanged state due to its own weight, as shown by solid lines in FIGS. 13 and 14. At this time, the fuel adsorption members 101 are arranged so as to face an outlet port 103 of a housing 104, and adsorb a fuel vapor leaking from the engine. Further, at an engine operating time when the intake air E exists, the fuel adsorption members 101 are deformed along a flow of the intake air E due to an application of the pressure of the intake air E, as shown by two-dot chain lines in FIGS. 13 and 14. At this time, the fuel adsorption members 101 allow an inflow of the intake air E to the outlet port 103.
In the air cleaner described in Japanese Laid-Open Patent Publication No. 2001-336454, a plurality of projections 112 are provided in an upper wall of a housing 111 while being spaced with each other, as shown in FIG. 15. A fuel adsorption member 113 is formed by applying a material to a gap between the projections 112 and an inner surface of the upper wall of the housing 111, and solidifying the applied material. The material forming the fuel adsorption member 113 is prepared by mixing a powdery active carbon to an acrylic based resin emulsion.
The air cleaner described in Japanese Laid-Open Patent Publication No. 2003-42017 is provided with a sheet-like fuel adsorption member 121, as shown in FIG. 16. The fuel adsorption member 121 is arranged downstream of a filter element 122, and is attached within a housing 123 in such a manner as to cut across a flow path of the intake air E (an air flow path).
However, in the structure shown in FIGS. 13 and 14, even if the fuel adsorption members 101 get out of the air flow path by the intake pressure, a part of the air flow path is obstructed by the fuel adsorption member 101, as shown by the two-dot chain line in the drawing. Accordingly, a ventilation resistance is increased, and there is a risk that a fuel consumption and an engine output are adversely affected. Further, the fuel adsorption members 101 repeat deformation in accordance with a fluctuation of an air flow, and the positions of the fuel adsorption members 101 are changed by little and little in accordance with a vibration of a vehicle or a fluctuation of an intake pressure. Accordingly, a fatigue is accumulated in the fuel adsorption members 101, and the fuel adsorption members 101 tend to be damaged at an early stage. Further, a wear powder of the active carbon tends to be generated by a friction between the active carbons and a friction between the active carbon and a fiber retaining the active carbon. For these reasons, not only a fuel adsorbing function of the active carbon is lowered, but also there is a risk that a fragment of the fuel adsorption members 101, the wear powder of the active carbon or the like is sucked into the engine so as to cause an engine malfunction.
Particularly, in the structure shown in FIG. 13, since the fuel adsorption member 101 is supported to the housing 104 only by an upper end thereof, the fuel adsorption member 101 tends to be damaged by an impact pressure of a backfire.
In the structure shown in FIG. 15, the fuel adsorption member 113 is formed by applying the emulsion to the upper wall of the housing 111. Accordingly, a reinforcing member for coping with the impact pressure and a heat of the backfire cannot be provided on a surface of the fuel adsorption member 113. Therefore, the surface of the fuel adsorption member 113 tends to be damaged by the impact pressure and the heat of the backfire. Further, in the fuel adsorption member 113, the active carbon having the fuel adsorbing function is buried in the resin. Accordingly, even if the resin formed of the emulsion is porous, the fuel adsorbing function of the active carbon is limited to a large degree because the surface of the active carbon is covered with the resin.
In the structure shown in FIG. 16, since the air flow path is obstructed by the fuel adsorption member 121, there is a risk that the ventilation resistance is increased, and the fuel consumption and the engine output are adversely affected. Even it the reinforcing means is provided in the fuel adsorption member 121, the fuel adsorption member 121 is directly exposed to the impact pressure of the backfire substantially on the entire surface thereof. Accordingly, the fuel adsorption member 121 tends to be damaged. In order to prevent this, the surface downstream of the fuel adsorption member 121 may be reinforced by a sheet. As a result, there is a high possibility that the ventilation resistance is further increased.
Therefore, in accordance with the conventional structures, it is impossible to sufficiently satisfy the demand for a reduction of the ventilation resistance, the fuel adsorbing function of the fuel adsorption member, and durability.